Method of maintaining a double circulation in oil wells



May 25,1926. 1,585,969

R. N. FERGUSON METHOD OF MAINTAINING A DOUBLE CIRCULTIION INIOIL WELLS Filed Oct. 24, 1923 25 'Ff'.f. '251 fnllllllllll A TTORAZYS,

Patented May 25, 1926.

gUNITED ls 'rfrizs BOY N. FERGUSON',4 OF LOS ANGELES, CALIFORNIA.

METHOD OF MAINTAINING A DOUBLE CIRCULATION IN OIL WELLS.

Application led October 24, 1923. Serial No. 670,506.

My invention relates to the art of .drilling oil wells and is particularly applicable to the drilling of wells by the rotary system.

In drilling wells by the rotary system, it is now common practice to rotate a string of drill pipe in the hole by means of a rotary ta le set upon the derrick floor. A heavy mud is forced downwardly through the drill pipe to the bit. .This mud serves to raise the cuttings produced Aby the bit to the surface. It also serves to lubrlcate the hole. It is also forced by the hydrostatic pressure back into the formations surrounding the hole, cementing up the walls of the well and helping to prevent them from eaving.

In the rotary system it is usually possible to drill an open hole for considerable distances. That is, it is possible to produce one or' two thousand feet of hole with no casing except perhaps two or three hundred feet at the extreme upper end of the hole. Sometimes, however, the forma tions are such that easing must be placed and cemented and the hole continued with a smaller diameter bit. If this occurs several times the hole gets so small that great difliculties are encountered in finishing the well and getting it on production.

It is an object of my invention to establish a methodby which a. well may be drilled by the rotary system using the usual circulation and, at the same time, casing may be carried, that is, hung in the hole to protect the walls thereof.

It is a further object of my invention to devise a method by which a double circulation may be `established in such a well, a slow circulation of heavy mud or other fluid being maintained outside the carried pipe and a faster circulation of water, mud, or other fluid being maintained through the drill pipe.

Further objects and advantages will be made evident hereinafter.'

Referring to the drawing which is for illustrative purposes only:

Fig. 1 is a side elevation partly in section of an oil well being drilled by my method.

Fig. 2 is a section on a plane indicated byy the line 2-2 ofv Fig. 1.

Fig. 3 is a diagram showing the method of operation of my invention.'

The form of apparatus best suited tol carry out my method comprises a short string of stove pipe casing 11 which extends down into the well for two or three hundred feet and which is preferably cemented in place at its lower end. This stove pi e casing is tightly secured at its upper en in a stove pipe casing head 12 through which casing 13 projects. :Surroundin the casin 13 inside the head 12 `is packing 14 which may be compressed by a gland 15 to make a lluid tight joint around the casing 13. A pipe 16 is threaded in the head 12 below the packing 14.

The casing 13 may be suspended by any convenient means. In the form shown a collar 17 of the casing 13 rests on top of the gland 15, the gland being preferably split to allow it to be removed and replaced.

At the upper end of the casing 13 is carried a easing head 20. The drill pipe 21 extends through the head 20. It is preferably suspended on a hollow square drill stem 22 which carries a swivel 23 at its upper end. The drill stem also extends through and is driven by a rotary table 29. The swivel 23 has a flexible water connection 24 and a bail 25 by which it may be suspended from the hoisting tackle of the well. The casing head 20 carries packing 26 which may be compressed by a split gland 27. A pipe 28 is connected into the casing head 20 below the packing 26.

An expanding bit 30 of any well known form is secured to the lower end of the drill pipe 21. The form shown consists of a body 31 carrying circular cutters 32 secured eccentrically on a pin 33. A water passage 31 extends through the body 31. lVhen this bit is drawn upwardly, the cutters 32 turn on the pin 33 into a position in which they may be pulled up into the pipe 13.

The method contemplated may be described as follows:

The parts of the apparatus being assembled as shown, the square stem 22 is rotated by the rotary table 29, thus rotating the drill pipe 21 and causing the bit 30 to make a hole. If the usual method of rotary drilling were followed, a heavy rotary `mud would be forced downwardly through the drill pipe 21 and we would depend on the cementing action of this mud to hold up the walls of the well. We would also utilize this mud to carry upwardly the cuttings from the bit.

The two functions of the ordinary rotary mud I prefer to separate, using one type of fluid to carry away the chips and another to support the walls of the well. To accomplish this I employ two separate and independent circulations.

The circulations can best be understood from Fig. 3. One circulation which may be called the drilling circulation is provided by a pump l10 delivering fluid under pressure through the flexibe hose 24. The fluid so deliver-ed asses downwardly through the hollow dri l stein 22 and the drill pipe 21 to the bottom of the hole and upwardly through the casing 13 and out through the pipe 28. It may then be delivered through a pipe 41 to a sump 42 by opening a. valve or through a pipe 44 to a sump 45 by opening a valve 46. The pump 40 may take fluid from the sump 45 through a pipe 47 having a valve 48 or it may be supplied independently through a pipe 49 having a valve 50. The drilling circulation may employ mud, water, oil or other fluid.

The other circulation which may be termed the sustaining circulation is maintained by a pump 55 which may take fluid from the sump 42 and deliver it through the pipe 16 into the space outside the casing 13. The fluid joins the drilling circulation at the bottom of the hole flowing upwardly inside the casing 13 and outside the drill pipe 21 and being delivered through the pipe 28 to either the sump 42 or the sump 45.

As the invention is usually practiced, the sustaining circulation will be a very heavy mud or in some cases a heavy crude oil. 'Due to its viscosity and body, it will require con siderable pressure to maintain this circulation although the liquid need not move rapidly. The sustaining circulation muds off the formations through which the well passes, serving to hold back any fluids in these formations and to prevent caving. It also keeps the casing 13 lubricated and prevents it freezing or sticking in the hole.

When operating with heavy mud for sustaining circulation and light mud or water for drilling circulation, it is possible to deliver the discharge'from the pipe 28 to a settlinoa tank or sump pulling the heavy mud from the bottom by the pump 55 and drawing the supernatant water from the top of the tank by the pump 40. When operating in this manner, it is desirable to put in separating means for removing the heavy chips from the discharge from the pipe 28 before this discharge is passed to the settling tank.

It will be seen that by establishing a slow sustaining circulation of heavy mud I am able to carry the casing 13 without danger of it sticking and by operating the drill pipe 2l inside this casing I protect the walls of the hole from the action of the drill pipe as well as protect the drill pipe from boulders or rock formations. By moving the heavy mud of the sustaining circulation slowly. I am able to use aliquid which is much heavier and more eflicient than any which could bev successfully used in the present method of operating.

Also, since the drilling circulation is not depended on to support the walls of the well but merely to soften the formations, to form mud, and to carry away the cuttings (in all of which functions it is assisted by the sustaining circulation), I am able to use water alone or a light mud which can be moved at high velocity and with great eiliciency.

I claim as my invention:

l. A method of drilling a well comprising: suspending a casing in the well; operating a cutting bit below the casing by means of drill pipe passing through the casing; and establishing a downward circulation respectively outside said casing and inside said drill pipe.

2. A method of drilling a well comprising: suspending a casing in the well; operating a cutting bit below the casing by means of drill pipe passing through the casing and while providing a drilling circulation through said bit; and establishing a sustaining circulation of liquid downwardly outside the casing and upwardly inside the casing. y

3. A method of drilling a well comprising: suspending a casing in the well; operating a cutting bit below the casingl by means of drill pipe passing through the casing; establishing a drilling circulation of fluid downwardly through said drill pipe and upwardly through-the space between said drill pipe and casing; and establishing a sustaining circulation of liquid through the space outside said casing, around the bottom of said casing, and inside said casin A method of drilling a well comprising: suspending a casing in the well; operating a cutting bit below the casing by means of drill pipe passing through the casing; establishing a drilling circulation of fluid downwardly through said drill pipe and upwardly through the space between said drill pipe and casing; and establishing a sustaining circulation of liquid downwardly outside the casing and upwardly inside the casing.

5. A method of drilling a well comprising: suspending a casing in the well; operating a cutting bit below the casing by means of drill pipe passing through the casing; establishing a drilling circulation of fluid downwardly through said drill pipe and upwardly through the space between said drill pipe and casing; and establishing a sustaining circulation of liquid through lthe space outside said casing, around the bottom of said casing, and inside said casing, said sustaining circulation being made up of a liquid o different physical consistency from the liquid forming the drilling circulation.

6. A method of drilling a well comprising: suspending a casing in the well; operating a cutting bit below the casing by means of -drill pipe passing through the casing; establishing a drilling circulation of uid downwardly through said drill pipe and upwardly through the s ace between said drill pipe and casing; an establishing a sustaini circulation of liquid downwardl outside the casing and upwardly inside t e casing, said sustainin circulation being made up of a li uid of di erent physical consistency from t e liquid forming the drilling circulation.

7. A method of drilling a well comprising: suspending a casin in the well; operating a -cutting bit be ow the casing by means of drill pipe passing through the casing; establishin a drilling circulation of fluid downward through said drill pipe and upwardly t rough the space between said drill pipe and casing; and establishing a sustaimng circulation of liquid through the space outside said casing, around the bottom of said casing, and inside said casing, said sustaining circulation being made up of a liquid which is of greater viscosity than the liquid forming the drilling circulation.

8. A method of drilling a well comprising: suspending a casing inthe well; operating a cutting bit below the casing by means of drill pipe passing through the casing; establishing a drilling circulation of fluid downwardly through said drill pipe and upwardly through the s ace between said drill pipe and casing; an establishing a sustaining circulation of liquid downwardl outside the casing and upwardly inside t e casing, said sustaining circulation being made up of a liquid which is of greater viscosity than the liquid forming the drilling circulation.

In testimony whereof, I have hereunto set my hand at Los Angeles, California, this 18th day of October, 1923.

ROY N. FERGUSON. 

